class Sequel::SQL::Expression

  1. lib/sequel/sql.rb
Superclass: Object

Base class for all SQL expression objects.


Public Class

  1. attr_reader
  2. comparison_attrs
  3. inherited

Public Instance

  1. ==
  2. clone
  3. eql?
  4. hash
  5. inspect

Public Instance Aliases

dup -> clone


comparison_attrs [R]

All attributes used for equality and hash methods.

Public Class methods


Expression objects are assumed to be value objects, where their attribute values can’t change after assignment. In order to make it easy to define equality and hash methods, subclass instances assume that the only values that affect the results of such methods are the values of the object’s attributes.

[show source]
   # File lib/sequel/sql.rb
92 def attr_reader(*args)
93   super
94   comparison_attrs.concat(args)
95 end

Copy the comparison_attrs into the subclass.

[show source]
    # File lib/sequel/sql.rb
 98 def inherited(subclass)
 99   super
100   subclass.instance_variable_set(:@comparison_attrs, comparison_attrs.dup)
101 end

Public Instance methods


Alias of eql?

[show source]
    # File lib/sequel/sql.rb
125 def ==(other)
126   eql?(other)
127 end

Make clone/dup return self, since Expression objects are supposed to be frozen value objects

[show source]
    # File lib/sequel/sql.rb
119 def clone
120   self
121 end

Returns true if the receiver is the same expression as the the other expression.

[show source]
    # File lib/sequel/sql.rb
131 def eql?(other)
132   other.is_a?(self.class) && !self.class.comparison_attrs.find{|a| public_send(a) != other.public_send(a)}
133 end

Make sure that the hash value is the same if the attributes are the same.

[show source]
    # File lib/sequel/sql.rb
136 def hash
137   ([self.class] +{|x| public_send(x)}).hash
138 end

Show the class name and instance variables for the object.

[show source]
    # File lib/sequel/sql.rb
141 def inspect
142   "#<#{self.class} #{{|iv| "#{iv}=>#{instance_variable_get(iv).inspect}"}.join(', ')}>"
143 end